1. Field of the Invention
The invention relates to a battery housing.
2. Description of the Related Art
The demands on battery housings are quite comprehensive. In the case of mobile applications, for example in the automotive sector, the battery cells or modules stored in the housing must be mechanically protected, for one thing against the vibration stress during usual driving operation. The battery cells or modules must also be mechanically protected in the event of damage to the vehicle and therefore perhaps also to the battery housing in the event of an accident. In many countries, complete encapsulation of the cells of a battery is furthermore required, in order to prevent battery fluids or reaction products from leaking in the event of damage, or to prevent the formation of reaction products. Ultimately, encapsulation also serves for fire protection, which is particularly relevant in the vehicle sector.
Particularly in connection with increasing electromobility, additional demands are made on such battery housings, in order to improve the useful lifetime but also the performance capacity of the batteries used. Even today, it must be ensured that the battery cells accommodated in the battery housing do not cool down to such an extent that the electrochemical processes that occur in the battery freeze. Furthermore, however, the battery housing must also ensure that any excess heat that might occur, for example while carrying out a quick-charging process of the battery or in the event of increased consumption of power from the battery, is reliably dissipated. In summary, these demands mean that within a battery housing that meets current requirements, the temperature must be maintained within an average permissible range, in other words is not allowed to drop below a defined lower temperature, but also not allowed to exceed a defined upper temperature limit. In the future, it will therefore be necessary to provide intelligent battery housings with intelligent temperature management.
From the state of the art, it is known to connect individual battery cells to form groups and to combine them into modules. These modules are mostly provided with simple thermal insulation, wherein this insulation mostly involves pre-molded polystyrene housings. To dissipate heat, cooling surfaces between the individual cells, through which cooling water flows, can be integrated into these housings. In general, in the automotive sector multiple such modules are combined to form a total battery. This total battery is then often installed into a trough-shaped battery housing, which is supposed to ensure fixation of the total battery in the vehicle, for one thing, and is supposed to provide the required crash safety, for another thing.
For this purpose, a battery housing for accommodating a battery module of a vehicle is previously known from DE 40 13 269 A1, wherein this battery housing is configured as a rigid structural element, and the wall elements of the battery housing are configured in double-walled manner, in each instance, i.e. in a sandwich design with an inner wall and an outer wall disposed at a distance from the former. The interstice between the inner and outer walls is filled with a porous insulation material in this embodiment, in each instance, and subsequently evacuated. It is doubtful, however, whether this porous insulation material is configured to be pressure-resistant, and accordingly whether the previously known battery housing actually has the required crash safety. Furthermore, cooling of the storage cells that form the battery, by means of latent heat storage units, is not implemented in the wall of the battery housing. Instead, the latent heat storage units used for cooling are disposed in the interstices between the storage cells.
A further battery housing for accommodating a battery module of a vehicle is known from EP 0 588 004 A1. In this connection, the battery housing is configured as a rigid structural element. The wall elements of the battery housing are configured in double-walled manner, in each instance, i.e. also in a sandwich design with an inner wall and an outer wall disposed at a distance from the former. The interstice between these inner and outer walls is filled with a porous support material. The cooling elements used for cooling are also disposed in this interstice. This housing, however, is irreversibly connected with the battery cell disposed in the housing, which is produced in a layer structure, comprising, from the outside to the inside, an insulation layer, a heat storage layer, and a cooling layer.
In this connection, a battery box module for a vehicle, particularly for a motor vehicle, is also known from DE 103 19 350 B4. This battery box module is a mechanically robust box for accommodating a vehicle battery and a lid that closes the box and can be released from the box, wherein the box has a trough-like double-wall design with switchable vacuum insulation, which can be switched into a thermal transient state and a thermal insulation state, wherein the module additionally comprises an electrical controller, which is responsible for switching the vacuum insulation.
The trough-like design of the battery box module is supposed to contribute to making it possible to capture at least small amounts of leaking battery acid.
Switchable vacuum insulation is supposed to be understood to mean that when the vacuum insulation is in a non-switched or current-free state, the insulation state of the battery housing is maintained, in other words heat insulation of the battery is present. In addition, however, the vacuum insulation can be switched as a function of the battery temperature and/or of the ambient temperature and/or of the power intensity or other external demands, and it can thereby be put into a thermal transient state.
For this purpose, an activatable material is disposed in the double wall of the battery box, which is understood to mean that a heat insulation material, for example tempered glass fiber board, is introduced into the double wall of the previously known battery box module, and furthermore the inner space is evacuated, in order to thereby produce low heat conductivity.
In addition, a metal hybrid getter is integrated into the interior of this insulation. This getter is able to store hydrogen at temperatures below approximately 100° C. When the getter is heated, a hydrogen atmosphere can thereby be produced in the heat insulation. This hydrogen atmosphere, in combination with the glass fiber board, leads to a significant increase in heat conductivity. This state is then referred to as a transient state of the heat insulation.